A CMP (Chemical Mechanical Polishing) method is conventionally used in a processing technique of a semiconductor device as a technique to flatten a semiconductor wafer. In the CMP method, improvement in productivity such as throughput or cost is demanded and processing accuracy such as in-plane uniformity or flatness of the semiconductor wafer is also demanded.
For example, in a solid memory having a three-dimensional structure, a protection film or the like includes large concaves and convexes and steps to be flattened are large. In such a case, the film thickness of the protection film or the like to be polished is increased, which prolongs the polishing time. As a result, the throughput is adversely lowered.
In connection thereto, a method of implanting ions into a polishing target film is known as means for increasing the polishing rate. By polishing the polishing target film after implanting ions into the entire surface of the polishing target film or selectively implanting ions into convex portions of the polishing target film, the polishing rate of portions of the polishing target film into which the ions have been implanted can be increased.
However, these methods have problems such as an insufficient polishing rate and degradation in the in-plane uniformity of the semiconductor wafer after polishing.